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Increasing number of ports by stacking 2950 and 2960 switches

r.brandenburg
Level 1
Level 1

Need some advice:

We have a small isolated lab environment network, i.e. only machines connected to the network are visible, no external connections.

We currently have a WS-C2950T-48-SI and as the number of machines connected will be increasing soon we will need more than the 48 ports provided by the 2950 switch.

I see that the max ports is on most Cisco switches is 48, so thinking that we should stack another switch on the network in order to add more ports.

Can we stack a 2950 with the recommended replacement, the WS-C2960-48TT-L. If so, is there any documentation on how to connect the two?

The goal would be to make a stack that would appear as a single IP for control purposes.

We currently configure the existing 2950 switch into multiple VLANS, so will need to maintain that capability to create VLANS across the 2 switches.

Thanks in advance for any help.

25 Replies 25

Edison Ortiz
Hall of Fame
Hall of Fame

You won't be able to stack them but you can cluster them, please refer to the documentation:

http://www.cisco.com/en/US/docs/switches/lan/catalyst2960/software/release/12.2_55_se/configuration/guide/swclus.html

Thanks for the quick reply. Clustering sounds like the way to go based on the doc link you supplied. 

Another quick question; as I read it, sounds like a cluster is not required to have a cluster standby switch. Sounds optional.

Thanks again.

To be honest, I suggest following the documentation and based your design on trial and error.

Very few companies, if any, are going with clustering switches design anymore.

I can't offer much guidance on caveats presented when clustering, sorry.

manju.cisco
Level 3
Level 3

Hi Randy,

2950/60 are not stackable switches.

However 2960-S can use FlexStack to add switches into stack, but doesn't behave like StackWise which is in 3750 stackable switches.

Thanks,

Manju

Leo Laohoo
Hall of Fame
Hall of Fame

I agree with Edison's post.  Your only option is "clustering" but even then, I don't see any reason to do so.

The only convinience with "clustering" is when you are have limited amount of management IP address.  Otherwise, this is no longer applicable in modern day technology.

r.brandenburg
Level 1
Level 1

For our small network we really only need a managed switch that has more than 48 ports. I need to be able to create multiple VLANs. We already have the 2950 switch, so thought the best way to extend it to more ports would be to stack (or cluster). If there is a simpler option that will still allow me to create multiple VLANs across the 2 switches, I am all for it.

Randy Brandenburg wrote:

For our small network we really only need a managed switch that has more than 48 ports. I need to be able to create multiple VLANs. We already have the 2950 switch, so thought the best way to extend it to more ports would be to stack (or cluster). If there is a simpler option that will still allow me to create multiple VLANs across the 2 switches, I am all for it.

You can deploy multiple switches in your network supporting multiple Vlans without the need for clustering.

Clustering allows you to assign one IP address to all switches for centralized management.

You can still achieve the same functionality (multiple vlans, multiple switches)

by having each switch with an unique IP address and manage them independently.

While on the subject of creating multiple Vlans, please do not consider using VTP Server/Client model.

Change your VTP mode to transparent and manually create the Vlans on each of the physical switches.

The Server/Client model can create outages in your network rather easily because any switch can assume

a VTP Server role and can potentially wipe out the Vlan from other production switches.

Regards,

Edison

 I need to be able to create multiple VLANs.

Ummmm ... who's doing the routing?  I mean, granted, the 2960/2960G/2960S can perform "limited" routing but you still need something route traffic from one VLAN to another.

2960S is, in my opinion, the most affordable Layer 2 switch that will do stacking (it's better than clustering).

A few caveats umptor:

1.  Stack backplane is 10Gbps, full duplex;

2.  You CANNOT stack 5 or more (maximum stacking limit is 4); and

3.  You can stack only 2960S.  You cannot stack 2960S with, say, 2960 or 2960G or 3560 (all models) or 3750 (all models) and definitely NOT the 4500 and 6500.

r.brandenburg
Level 1
Level 1

Thanks for the discussion; After browsing the Catalyst 2960 and 2960-S Switches Software Configuration Guide sections about creating VLANs and about creating a trunk interface port between switches, I think I have a basic undertsanding of how to proceed with/without clustering the switches. As Edison suggests, it will take some trial and error, but the basic requirements I have should be attainable.

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Generally, you can just connect one switch to another to increase available ports.  If they are manageable switches, you have more "devices" to configure vs. actual stacked (or clustered) switches.

When you connect switches, you can get into other considerations such as bandwidth between switches, extending VLANs, redundancy, and optimal (fewest) hops between devices.  But for just two switches, you might not need to consider any of this.

r.brandenburg
Level 1
Level 1

Anyone have a feel for the performance difference between a 2 switch cluster and a 2 switch stack? If any?

Also, can a cluster of  2960 switches be configured via SSH? I see references to configuring via CLI, so assume SSH is possible, just as a console cable or telnet?

Thank you.

Anyone have a feel for the performance difference between a 2 switch cluster and a 2 switch stack? If any?

Like I've said before, "clustering" is old-school.  Other than the fact that the only major benefit with "clustering" is the usage of management IP addresses.  This is the same with switch stacking (like the 2960S and the 3750 family).

The downside with "clustering" is the size of your uplink to cluster one from the other.  So if your switch is clustered using 100 Mbps then this is your cluster "speed".  If you have 1000 Mbps then this is your cluster "speed".  With stacking, it is far superior.  How?

1.  Your backplane stacking is between 10 Gbps (2960S), 16 Gbps (3750, 3750G) or 32 Gbps (3750E/3750X) full duplex; and

2.  Configuration management - With switch stack, you configure your entire stack from the master switch stack or from one logical unit.  With switch clustering, you configure each individual cluster member separately.

This is the main reason why people who's have experience with "clustering" will readily dump this in favour of switch clustering.  (Heck, some people may just feign "ignorance" when asked this question!)

Also, can a cluster of  2960 switches be configured via SSH? I see references to configuring via CLI, so assume SSH is possible, just as a console cable or telnet?

Yes, you can configure a cluster of plain 2960 from SSH provided you are running "Crypto" IOS and have SSH enabled.  You can do so either console and/or Telnet.  Again, because you are dealing with "clustering" you may need to configure each individual cluster member for SSH.

r.brandenburg
Level 1
Level 1

Thanks for taking the time to answer my questions. I want to understand this completely so please bear with me - I was thrust into this switch research with very little experience (if you couldnt tell)....

So, on a cluster of 2 switches, the max switching speed between the 2 switches would be the speed of the port that I connect the 2 switches together (e.g., one of the G-bit ports). So traffic from devices connected to a port on switch A (100 Mbps)  to a device on switch B (also connected on the 100Mbps port), would effectovely be 100Mbps (max of 1000Gbps).

The only thing that is making me cling to the clustering setup is cost. I need to buy 16 switches (will connect 2 per site). Expansion above 2 switches per site is very -very unlikely. Also, all network traffic will be local to the 2 switches which will be installed in a isolated lab environment with all machines are on the same subnet. 

I will suggest going with the 2960-S, so that if needed in the future, we can stack them, but will probably use clustering for now. I think buying the stack modules in addition to the switches would be cost prohibitive for our project.

So traffic from devices connected to a port on switch A (100 Mbps)  to a device on switch B (also connected on the 100Mbps port), would effectovely be 100Mbps (max of 1000Gbps).

Remember the devices that are connected to switch A has to SHARE the bandwidth of the uplink.  For instance, your devices/clients in Switch A are connected to 1 Gbps interface and your uplink are two  1 Gbps interface.   IT's OK if the traffic is sporadic, but what if people are sending large chunks of files to and from each other or watching HD video?

The only thing that is making me cling to the clustering setup is cost. I need to buy 16 switches (will connect 2 per site). Expansion above 2 switches per site is very -very unlikely. Also, all network traffic will be local to the 2 switches which will be installed in a isolated lab environment with all machines are on the same subnet.

I honestly don't have any idea what is the maximum number of switches you can "cluster" nowadays.  Back then it was limted to the GigaStacking GBIC cable.  But stacking 16 switches is a very, very, very, very bad design.  Heck, stacking more than 9 is just, for the lack of a better word, dumb.  (Sorry for my choice of word.)

The only thing that is making me cling to the clustering setup is cost.

Then why bother stacking?  Why don't you just give each of your switches a management IP address, put them all in one VLAN and be done?   Ensure your uplinks are all in a trunk.

I will suggest going with the 2960-S, so that if needed in the future, we can stack them, but will probably use clustering for now. I think buying the stack modules in addition to the switches would be cost prohibitive for our project.

Talk to the local Cisco office (not your local authorized Cisco reseller).  There are so many ways for you to get discounts from Cisco.

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